Curable resin composition

ABSTRACT

The present invention provides a curable resin composition comprising:  
     (A) an acryl resin having (a) a carboxyl group originating in a carboxyl group-containing polymerizable unsaturated monomer selected from acrylic acid, methacrylic acid, maleic acid and itaconic acid and (b) a carboxyl group originating in a carboxyl group-containing polymerizable unsaturated monomer having a polymerizable carbon-carbon double bond and a carboxyl group separated from the double bond by at least 6 carbon atoms,  
     (B) an epoxy group-containing acryl resin and  
     (C) a curing catalyst.

TECHNICAL FIELD

[0001] The present invention relates to a curable resin composition of aso-called “acid-epoxy base” which is cured by cross-linking reactionbetween a carboxyl group and an epoxy group, particularly to a curableresin composition which is excellent in a storage stability and anelectrostatic coating property and which can form a coating filmexcellent in a scratch resistance and a heat yellowing resistance. Theabove curable resin composition can suitably be used as a top coatingmaterial for car bodies.

BACKGROUND ART

[0002] Carboxyl group-containing vinyl resins, vinyl resins having anepoxy group and a hydroxyl group and curable resin compositions of anacid-epoxy base containing a curing catalyst have already been known,and used as the above carboxyl group-containing vinyl resin is a resinobtained by copolymerizing a carboxyl group-containing polymerizablemonomer with a polymerizable monomer having an acid anhydride group toobtain a vinyl resin and semi-esterifying the acid anhydride groupscontained in the vinyl resin with monoalcohol (refer to, for example,U.S. Pat. No. 5,508,352 or European Patent Publication No.EP-A-667,371).

[0003] The present inventors have investigated in detail theperformances of the curable resin composition described above, and ithas become clear that a coating film formed from the above resincomposition is excellent in an acid resistance, a coating film hardnessand a scratch resistance but there is the defect that a storagestability and an electrostatic coating property of the composition and aheat yellowing resistance of the coating film are still poor in terms ofpractical use.

[0004] An object of the present invention is to solve the defectdescribed above without reducing the performances of a coating film suchas an acid resistance, a coating film hardness and a scratch resistancein a conventional acid-epoxy base curable resin composition.

[0005] Intensive researches repeated by the present inventors haveresulted in finding that the object described above can be achieved byusing as a carboxyl group-containing resin, a specific acryl resinhaving a carboxyl group originating in a carboxyl group-containingpolymerizable unsaturated monomer selected from acrylic acid,methacrylic acid, maleic acid and itaconic acid and a carboxyl grouporiginating in a carboxyl group-containing polymerizable unsaturatedmonomer having a polymerizable carbon-carbon double bond and a carboxylgroup separated from the double bond by at least 6 carbon atoms, andthey have come to complete the present invention.

DISCLOSURE OF THE INVENTION

[0006] Thus, provided according to the present invention is a curableresin composition (hereinafter referred to as the “present composition1”) comprising:

[0007] (A) a carboxyl group-containing acryl resin having (a) a carboxylgroup originating in a carboxyl group-containing polymerizableunsaturated monomer selected from acrylic acid, methacrylic acid, maleicacid and itaconic acid and (b) a carboxyl group originating in acarboxyl group-containing polymerizable unsaturated monomer having apolymerizable carbon-carbon double bond and a carboxyl group separatedfrom the double bond by at least 6 carbon atoms,

[0008] (B) an epoxy group-containing acryl resin and

[0009] (C) a curing catalyst.

[0010] Further, provided according to the present invention is a curableresin composition (hereinafter referred to as the “present composition2”) comprising:

[0011] (D) a carboxyl group-containing acryl resin having (a) a carboxylgroup originating in a carboxyl group-containing polymerizableunsaturated monomer selected from acrylic acid, methacrylic acid, maleicacid and itaconic acid, (b) a carboxyl group originating in a carboxylgroup-containing polymerizable unsaturated monomer having apolymerizable carbon-carbon double bond and a carboxyl group separatedfrom the double bond by at least 6 carbon atoms and (e) a carboxyl grouporiginating in a semi-esterification product of a polymerizableunsaturated dibasic acid anhydride,

[0012] (B) an epoxy group-containing acryl resin and

[0013] (C) a curing catalyst.

[0014] The present composition 1 and the present composition 2 shall beexplained below in further details.

DETAILED DESCRIPTION OF THE INVENTION Present Composition 1

[0015] The present composition 1 provided by the present invention is acurable resin composition comprising a carboxyl group-containing acrylresin (A), an epoxy group-containing acryl resin (B) and a curingcatalyst (C) which shall be described below.

Carboxyl Group-Containing Acryl Resin (A)

[0016] The carboxyl group-containing acryl resin (hereinafter referredto as the “component (A)”) constituting the present composition 1 is anacryl resin having in a molecule, (a) a carboxyl group originating in acarboxyl group-containing polymerizable unsaturated monomer selectedfrom acrylic acid, methacrylic acid, maleic acid and itaconic acid and(b) a carboxyl group originating in a carboxyl group-containingpolymerizable unsaturated monomer having a polymerizable carbon-carbondouble bond and a carboxyl group separated from the double bond by atleast 6 carbon atoms.

[0017] The above component (A) can be obtained by, for example,copolymerizing (a) a carboxyl group-containing polymerizable unsaturatedmonomer selected from acrylic acid, methacrylic acid, maleic acid anditaconic acid, (b) a carboxyl group-containing polymerizable unsaturatedmonomer having a polymerizable carbon-carbon double bond and a carboxylgroup separated from the double bond by at least 6 carbon atoms and (c)an acryl base monomer.

[0018] The monomer (a) is a polymerizable monomer selected from acrylicacid, methacrylic acid, maleic acid and itaconic acid, and they can beused alone or in combination of two or more kinds thereof.

[0019] The monomer (b) is a carboxyl group-containing polymerizableunsaturated monomer having a polymerizable carbon-carbon double bond anda carboxyl group separated from the double bond by at least 6 carbonatoms, preferably 6 to 25 carbon atoms and more preferably 6 to 20carbon atoms. In the monomer (b), an atomic group formed by at least 6carbon atoms present between the polymerizable carbon-carbon double bondand the carboxyl group by may be linear or branched or may have analicyclic structure or an aromatic structure.

[0020] In this case, the “polymerizable carbon-carbon double bond” is apolymerizable group represented by —C═C—, and the carboxyl group can berepresented by —COOH. Carbon atoms contained in the above groups are notincluded in “at least 6 carbon atoms”. On the other hand, carbon atomscontained in an “ester bond” which is present in an atomic group betweenthe polymerizable carbon-carbon double bond and the carboxyl group areincluded in “at least 6 carbon atoms”.

[0021] The above monomer (b) can readily be prepared by any of thefollowing methods (1) to (3).

[0022] (1) A method in which lactones are subjected to ring-openingesterification with acrylic acid and/or methacrylic acid (hereinafterreferred as “(meth)acrylic acid”.

[0023] Lactones are cyclic compounds having an ester group in a ring andinclude the compounds having 3 to 17 rings, and, for example, α-lactone,β-lactone, γ-lactone, δ-lactone and ε-lactone can suitably be used. Thering-opening esterification of (meth)acrylic acid with lactones can becarried out by a conventionally known method, and the number of carbonatoms contained an atomic group between the polymerizable carbon-carbondouble bond and the carboxyl group can optionally be controlled bychanging the kind and the amount of the lactones used.

[0024] (2) A method in which a terminal hydroxyl group of a productobtained by subjecting (meth)acrylic acid to esterification with glycolsin almost the same mole ratio is subjected to semi-esterification withdicarboxylic acids in almost the same mole ratio.

[0025] The number of carbon atoms contained in an atomic group betweenthe polymerizable carbon-carbon double bond and the carboxyl group canreadily be controlled by the number of carbon atoms contained in theglycols and the dicarboxylic acids.

[0026] The glycols used in the method (2) described above are compoundshaving two hydroxyl groups in a molecule and include, for example,aliphatic glycols such as ethylene glycol, propylene glycol, diethyleneglycol, trimethylene glycol, tetraethylene glycol, triethylene glycol,dipropylene glycol, butanediol, methyl-butanediol, pentanediol,dimethyltrimethylene glycol, tetramethylene glycol, methyl-pentanediol,trimethyl-pentanediol, hexanediol, cyclohexanediol,cyclohexanedimethanol, neopentyl glycol and hydroxypivalic acidneopentyl glycol ester; alicyclic glycols such as cyclohexanedimethanol,trichlorodecanedimethanol, hydrogenate bisphenol A, hydrogenatebisphenol F and alkylene oxide adducts thereof, aromatic glycols such asbisphenol A, bisphenol F and alkylene oxide adducts thereof, polyesterglycols such as bis(hydroxyethyl) terephthalate; polyether glycols suchas polyethylene glycol, polypropylene glycol and polybutylene glycol;and polylactone glycols obtained by adding lactones such asε-caprolactone to the above glycols.

[0027] (Meth)acrylic acid can be reacted with the glycols by subjectingboth components to esterification in almost the same mole ratio by aknown method. The monomer (b) can be obtained by subjecting a hydroxylgroup contained in the product thus obtained to semi-esterification withdicarboxylic acids in almost the same mole ratio.

[0028] The dicarboxylic acids described above are compounds having twocarboxyl groups in a molecule and include, for example, aromaticdicarboxylic acids such as terephthalic acid, isophthalic acid, phthalicacid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid anddiphenylmethanedicarboxylic acid and anhydrides thereof, alicyclicdicarboxylic acids such as hexahydroisophthalic acid,hexahydroterephthalic acid, hexahydrophthalic acid andtetrahydrophthalic acid and anhydrides thereof; and aliphaticdicarboxylic acids such as adipic acid, sebacic acid, suberic acid,succinic acid, glutaric acid, maleic acid, chloromaleic acid, fumaricacid, dodecanoic diacid, pimelic acid, azelaic acid, itaconic acid,citraconic acid and dimer acid and anhydrides thereof.

[0029] (3) A method for subjecting a hydroxyl group-containingpolymerizable unsaturated monomer to semi-esterification with saturateddicarboxylic acids.

[0030] The hydroxyl group-containing polymerizable unsaturated monomeris a compound having each one polymerizable carbon-carbon double bondand one carboxyl group in a molecule and include, for example,monoesterified products of (meth)acrylic acid and glycols such asalkylene glycols having 2 to 20 carbon atoms and polyether glycols, suchas hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropylacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate andhydroxybutyl methacrylate.

[0031] The saturated dicarboxylic acids are compounds containing nopolymerizable unsaturated bond and having two carboxyl groups in amolecule and include, for example, aromatic dicarboxylic acids such asterephthalic acid, isophthalic acid, phthalic acid,naphthalenedicarboxylic acid, biphenyldicarboxylic acid anddiphenylmethanedicarboxylic acid and anhydrides thereof, alicyclicdicarboxylic acids such as hexahydroisophthalic acid,hexahydroterephthalic acid, hexahydrophthalic acid andtetrahydrophthalic acid and anhydrides thereof, and aliphaticdicarboxylic acids such as adipic acid, sebacic acid, suberic acid,succinic acid, glutaric acid, dodecanoic diacid, pimelic acid, azelaicacid and dimer acid and anhydrides thereof. Among them, dicarboxylicanhydrides are preferred.

[0032] It is estimated that the semi-esterification is carried out byreacting one of two carboxyl groups contained in the saturateddicarboxylic acids with one hydroxyl group of the hydroxylgroup-containing polymerizable unsaturated monomer in a proportion ofone mole of the saturated dicarboxylic acids to one mole of the hydroxylgroup-containing polymerizable unsaturated monomer. If the saturateddicarboxylic acids are anhydrides, ring-opening esterification iscarried out.

[0033] Esters of (meth)acrylic acid other than the monomers (a) and (b)described above are included in the acryl base monomer (c) used forproducing the component (A). They include, for example, alkyl esters orcycloalkyl esters having 1 to 24 carbon atoms with (meth)acrylic acid,such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropylacrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octylacrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexylacrylate, methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, isopropyl methacrylate, butyl methacrylate, hexylmethacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decylmethacrylate, lauryl methacrylate, stearyl methacrylate and cyclohexylmethacrylate; and alkoxyalkyl esters having 2 to 18 carbon atoms with(meth)acrylic acid, such as methoxybutyl acrylate, methoxybutylmethacrylate, methoxyethyl acrylate, methoxyethyl methacrylate,ethoxybutyl acrylate and ethoxybutyl methacrylate.

[0034] The component (A) can be obtained by copolymerizing the monomer(a), the monomer (b) and the acryl base monomer (c) each describedabove, and the other polymerizable monomer (d) than the above monomersmay be copolymerized therewith if necessary.

[0035] The other polymerizable monomer (d) include those given below asexamples.

[0036] (i) Hydroxyl group-containing polymerizable monomer: C₂ to C₈hydroxyalkyl esters of (meth)acrylic acid, such as hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl(meth)acrylate; monoesters of polyetherpolyols such as polyethyleneglycol, polypropylene glycol and polybutylene glycol with unsaturatedcarboxylic acids such as (meth)acrylic acid; monoethers ofpolyetherpolyols such as polyethylene glycol, polypropylene glycol andpolybutylene glycol with hydroxyl group-containing unsaturated monomerssuch as 2-hydroxyethyl (meth)acrylate; adducts of α,β-unsaturatedcarboxylic acids and monoepoxy compounds such as Cardula E10(manufactured by Shell Chemical Co., Ltd.) and α-olefin epoxide; adductsof glycidyl (meth)acrylate and monobasic acids such as acetic acid,propionic acid, t-butylbenzoic acid and fatty acids; monoesterifiedproducts or diesterified products of acid anhydride group-containingunsaturated compounds such as maleic anhydride and itaconic anhydridewith glycols such as ethylene glycol, 1,6-hexanediol and neopentylglycol; hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether; andallyl alcohol.

[0037] (ii) Fluorine-containing polymerizable monomer: perfluoroalkyl(meth)acrylates such as perfluorobutylethyl (meth)acrylate,perfluoroisononylethyl (meth)acrylate and perfluorooctylethyl(meth)acrylate.

[0038] (iii) Aromatic polymerizable monomer: styrene, α-methylstyrene,vinyltoluene and α-chlorostyrene.

[0039] (iv) Nitrogen-containing polymerizable monomer:nitrogen-containing alkyl (meth)acrylate such as N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl (meth)acrylate andN-t-butylaminoethyl (meth)acrylate; (meth)acrylamides such asacrylamide, methacrylamide, N-methyl(meth)acrylamide,N-ethyl(meth)acrylamide, N-methylol(meth)acrylamide,N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide,N,N-dimethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamideand N,N-dimethylaminoethyl(meth)acrylamide; aromatic nitrogen-containingmonomer such as 2-vinylpyridine and 1-vinyl-2-pyrrolidone; acrylonitrileand allylamine.

[0040] The component (A) can be obtained by using (a) the carboxylgroup-containing polymerizable unsaturated monomer selected from acrylicacid, methacrylic acid, maleic acid and itaconic acid, (b) the carboxylgroup-containing polymerizable unsaturated monomer having apolymerizable carbon-carbon double bond and a carboxyl group separatedfrom the double bond by at least 6 carbon atoms and (c) the acryl basemonomer as the essential components and, if necessary, (d) the otherpolymerizable unsaturated monomer and copolymerizing these monomers by aconventional solution radical polymerization method.

[0041] The use proportions of these respective monomers shall notstrictly be restricted and can optionally be selected according to theuse purposes of the present composition 1. In general, the monomer (a)can be used in such a proportion that an acid value based on the monomer(a) of the component (A) formed falls in a range of 30 to 150 mg KOH/g,particularly 40 to 120 mg KOH/g and further particularly 50 to 120 mgKOH/g, and the monomer (b) can be used in such a proportion that an acidvalue based on the monomer (b) of the component (A) formed falls in arange of 30 to 170 mg KOH/g, particularly 40 to 140 mg KOH/g and furtherparticularly 40 to 120 mg KOH/g. Also, the total acid value of the acidvalue based on the monomer (a) and the acid value based on the monomer(b) falls preferably in a range of usually 100 to 200 mg KOH/g,particularly 130 to 180 mg KOH/g and further particularly 140 to 170 mgKOH/g. Further, the monomer (c) is used in a proportion falling suitablyin a range of usually 10 to 80% by weight, particularly 20 to 70% byweight and further particularly 30 to 50% by weight based on the totalamount of the monomers (a), (b) and (c). On the other hand, the monomer(d) is used in a proportion falling suitably in a range of usually 100parts by weight or less, particularly 1 to 50 parts by weight andfurther particularly 5 to 20 parts by weight per 100 parts by weight ofthe total amount of the monomers (a), (b) and (c).

[0042] The component (A) thus obtained has preferably a hydroxyl valuefalling in a range of usually 0 to 50 mg KOH/g, particularly 0 to 30 mgKOH/g and a weight average molecular weight falling in a range of 2000to 50000, particularly 3000 to 25000.

[0043] In producing the component (A) by using the monomer (a), themonomer (b) and the monomer (c) and, if necessary, the polymerizablemonomer (d) and copolymerizing them, the plural monomers (b) in which anatomic group present between a polymerizable carbon-carbon double bondand a carboxyl group has a carbon atom number of at least 6, preferably6 to 25 and in which the carbon atom numbers are different from eachother can be used in combination, if necessary, as the monomer (b).

[0044] A difference in the carbon atom numbers of the atomic groupspresent in the plural monomers (b) in which the above carbon atomnumbers are different from each other falls preferably in a range ofusually at least 1, particularly 2 to 10. Thus, assuming, for example,that the monomer in which an atomic group has a small carbon atom numberis (b-1) and that the monomer in which an atomic group has a largecarbon atom number is (b-2), the atomic group present in the monomer(b-2) has preferably a carbon atom number falling in a range of 10 to25. On the other hand, the monomer in which an atomic group has asmaller carbon atom number by at least one, particularly 2 to 10 thanthat of the above monomer is preferably used as the monomer (b-1).

[0045] That is, capable of being also used as the component (A) is acarboxyl group-containing acryl resin obtained by using (a) the carboxylgroup-containing polymerizable unsaturated monomer selected from acrylicacid, methacrylic acid, maleic acid and itaconic acid, (b-1) thecarboxyl group-containing polymerizable unsaturated monomer in which anatomic group present between a polymerizable carbon-carbon double bondand a carboxyl group has a smaller carbon atom number by at least one,particularly 2 to 10 than that of the monomer (b-2) described below,(b-2) the carboxyl group-containing polymerizable unsaturated monomer inwhich an atomic group present between a polymerizable carbon-carbondouble bond and a carboxyl group has a carbon atom number of 10 to 25and (c) the acryl base monomer and, if necessary, (d) the otherpolymerizable unsaturated monomer than the monomers described above andcopolymerizing them. In this respect, a use proportion of the monomer(b-1) and the monomer (b-2) shall not strictly be restricted. Ingeneral, that of the monomer (b-1) falls suitably in a range of 10 to90% by weight, particularly 30 to 70% by weight based on the totalamount of the monomer (b-1) and the monomer (b-2), and that of themonomer (b-2) falls suitably in a range of 90 to 10% by weight,particularly 70 to 30% by weight.

[0046] Further, it is possible that prepared are the plural monomers (b)in which an atomic group present between a polymerizable carbon-carbondouble bond and a carboxyl group has a carbon atom number of at least 6,preferably 6 to 25 and in which the carbon atom numbers are differentfrom each other, for example, the monomer (b-1) and the monomer (b-2)each described above; the monomer (b-1) and the monomer (b-2) each arecopolymerized separately with the monomer (a) and the monomer (c) and,if necessary, the other monomer (d) than the monomers described above toproduce plural acryl resins (A); and they are used in a mixture. To bespecific, capable of being used as the component (A) is a mixture of acarboxyl group-containing acryl resin (A-1) obtained by using themonomer (a), the monomer (b-1) and the monomer (c) and, if necessary,the other monomer (d) than the monomers described above andcopolymerizing them and a carboxyl group-containing acryl resin (A-2)obtained by using the monomer (a), the monomer (b-2) and the monomer (c)and, if necessary, the other monomer (d) than the monomers describedabove and copolymerizing them.

[0047] The proportions of the respective monomers constituting the acrylresin (A-1) and the acryl resin (A-2) can be those described above.Further, in respect to a mixed proportion of both of these resins, thatof the acryl resin (A- 1) falls suitably in a range of 10 to 90% byweight, particularly 20 to 80% by weight based on the total solid matteramount of the resins (A-1) and (A-2), and that of the acryl resin (A-2)falls suitably in a range of 90 to 10% by weight, particularly 80 to 20%by weight.

[0048] Epoxy Group-Containing Acryl Resin (B):

[0049] The epoxy group-containing acryl resin (hereinafter referred toas the “component (B)”) constituting the present composition 1 is anacryl resin having at least one epoxy group and, if necessary, ahydroxyl group in a molecule.

[0050] The above component (B) can be obtained by copolymerizing anepoxy group-containing polymerizable monomer and an acryl base monomeras essential components and, if necessary, a hydroxyl group-containingpolymerizable monomer and/or the other polymerizable monomer.Preferably, the component (B) does not substantially contain a carboxylgroup.

[0051] The epoxy group-containing polymerizable monomer is a compoundhaving at least one epoxy group and at least one polymerizable doublebond respectively in a molecule and includes, for example, glycidylacrylate and glycidyl methacrylate.

[0052] The acryl base monomer is esters of (meth)acrylic acid other thanthe epoxy group-containing polymerizable monomer. It includes, forexample, alkyl esters or cycloalkyl esters having 1 to 24 carbon atomswith (meth)acrylic acid, such as methyl acrylate, ethyl acrylate,n-propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate,2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, laurylacrylate, stearyl acrylate, cyclohexyl acrylate, methyl methacrylate,ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, butylmethacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octylmethacrylate, decyl methacrylate, lauryl methacrylate, stearylmethacrylate and cyclohexyl methacrylate; and alkoxyalkyl esters having2 to 18 carbon atoms with (meth)acrylic acid, such as methoxybutylacrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethylmethacrylate, ethoxybutyl acrylate and ethoxybutyl methacrylate.

[0053] The hydroxyl group-containing polymerizable monomer is a compoundhaving at least one hydroxyl group and at least one polymerizable doublebond respectively in a molecule and includes, for example, C₂ to C₈hydroxyalkyl esters of (meth)acrylic acid, such as hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl(meth)acrylate; monoesters of polyetherpolyols such as polyethyleneglycol, polypropylene glycol and polybutylene glycol with unsaturatedcarboxylic acids such as (meth)acrylic acid; monoethers ofpolyetherpolyols such as polyethylene glycol, polypropylene glycol andpolybutylene glycol with hydroxyl group-containing unsaturated monomerssuch as 2-hydroxyethyl (meth)acrylate; adducts of α,β-unsaturatedcarboxylic acids and monoepoxy compounds such as Cardula E10(manufactured by Shell Chemical Co., Ltd.) and α-olefin epoxide; adductsof glycidyl (meth)acrylate and monobasic acids such as acetic acid,propionic acid, t-butylbenzoic acid and fatty acids; monoesterifiedproducts or diesterified products of acid anhydride group-containingunsaturated compounds such as maleic anhydride and itaconic anhydridewith glycols such as ethylene glycol, 1,6-hexanediol and neopentylglycol; hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether; andallyl alcohol.

[0054] The other polymerizable monomer is a compound having at least onepolymerizable unsaturated bond in a molecule other than the epoxygroup-containing polymerizable monomer, the acryl base monomer and thehydroxyl group-containing polymerizable monomer each described above. Tobe specific, capable of being suitably used are those selected from (ii)the fluorine-containing polymerizable monomer, (iii) the aromaticpolymerizable monomer and (iv) the nitrogen-containing polymerizablemonomer in “the other polymerizable monomer (d)” given as the example inthe explanation of the component (A) described above.

[0055] The component (B) can be obtained by using the epoxygroup-containing polymerizable monomer and the acryl base monomer as theessential components and, if necessary, the hydroxyl group-containingpolymerizable monomer and/or the other polymerizable unsaturated monomereach described above and copolymerizing these monomers by a conventionalsolution radical polymerization method.

[0056] The use proportions of the above monomers shall not strictly berestricted and can optionally be selected according to the use purposesof the present composition 1. To be specific, that of the epoxygroup-containing polymerizable monomer falls suitably in a range ofusually 20 to 85% by weight, particularly 30 to 70% by weight andfurther particularly 40 to 70% by weight, and that of the acryl basemonomer falls suitably in a range of usually 80 to 15% by weight,particularly 70 to 30% by weight and further particularly 60 to 30% byweight based on the total amount of the epoxy group-containingpolymerizable monomer and the acryl base monomer. The hydroxylgroup-containing polymerizable monomer is used preferably in an amountfalling in a range of usually 100 parts by weight or less, particularly10 to 60 parts by weight and further particularly 15 to 40 parts byweight per 100 parts by weight of the total amount of the epoxygroup-containing polymerizable monomer and the acryl base monomer, andthe other polymerizable unsaturated monomer is used preferably in anamount falling in a range of 100 parts by weight or less, particularly 1to 50 parts by weight and further particularly 3 to 30 parts by weightper 100 parts by weight of the total amount of the epoxygroup-containing polymerizable monomer and the acryl base monomer.

[0057] The component (B) thus obtained can have a weight averagemolecular weight falling in a range of 2000 to 50000, particularly 3000to 10000 and has preferably an epoxy equivalent falling in a range ofusually 50 to 1000, preferably 100 to 800. Further, the component (B)can have a hydroxyl value falling in a range of usually 10 to 300 mgKOH/g, particularly 40 to 150 mg KOH/g.

[0058] Curing Catalyst (C):

[0059] The curing catalyst (hereinafter referred to as the “component(C)”) constituting the present composition 1 is used in order toaccelerate cross-linking reaction of the component (B) with an epoxygroup, and to be specific, it includes, for example, phosphoric esterssuch as monobutyl phosphate, dimethyl phosphate, dibutyl phosphate,di-2-ethylhexyl phosphate and neopentyl glycol diglycidyl etherphosphate; quaternary ammonium salts such as tetrabutylammonium bromide,tetradodecyltrimethylammonium bromide and benzyltrimethylammoniumbromide; and phosphate base compounds such as tetrabutylphosphoniumsalts. Combined use of quaternary ammonium salts and phosphate basecompounds out of them elevates a storage stability of the presentcomposition 1 and therefore is preferred. A use proportion of thephosphate base compounds falls preferably in a range of usually 50 to150 parts by weight, particularly 60 to 130 parts by weight per 100parts by weight of the quaternary ammonium salt.

[0060] The present composition 1 can be prepared by mixing the component(A), the component (B) and the component (C) each described above in anorganic solvent. The mixing proportions of these respective componentscan optionally be selected according to the use purposes of the presentcomposition 1; in general, that of the component (A) falls suitably in arange of usually 20 to 80% by weight, particularly 30 to 70% by weightand further particularly 40 to 60% by weight based on the total solidmatter weight of the component (A) and the component (B); that of thecomponent (B) falls suitably in a range of usually 80 to 20% by weight,particularly 70 to 30% by weight and further particularly 60 to 40% byweight; and that of the component (C) falls preferably in a range ofusually 0.1 to 5 parts by weight, particularly 0.5 to 3 parts by weightand further particularly 1 to 2.5 parts by weight per 100 parts byweight of the total solid matter of the component (A) and the component(B).

[0061] The present composition 1 can be blended, if necessary, with ahydroxyl group-containing polyester resin, a solid color pigment, ametallic pigment, a light coherent pigment, an extender pigment, a UVabsorber, a light stabilizer, a coated face-controlling agent and aprecipitation inhibitor in addition to the component (A), the component(B) and the component (C).

[0062] Further, the present composition 1 can contain, in addition tothe component (A), the component (B) and the component (C), thefollowing component (E), that is, a carboxyl group-containing acrylresin which can be obtained by using the carboxyl group-containingmonomer (b) described above having a polymerizable carbon-carbon doublebond and a carboxyl group separated from the double bond by at least 6carbon atoms, the acryl base monomer (c) described above and asemi-esterification product (e) of a polymerizable unsaturated dibasicacid anhydride which shall be described later and, if necessary, theother polymerizable monomer (d) described above and copolymerizing thesemonomers by a conventional solution radical polymerization method.

[0063] The use proportions of these respective components in producingthe component (E) can optionally be selected according to the usepurposes of the present composition 1. In general, the monomer (e) canbe used in such a proportion that the acid value based on the monomer(e) of the component (E) formed falls in a range of 30 to 150 mg KOH/g,particularly 40 to 120 mg KOH/g and further particularly 50 to 100 mgKOH/g, and the monomer (b) can be used in such a proportion that theacid value based on the monomer (b) of the component (E) formed falls ina range of 30 to 170 mg KOH/g, particularly 40 to 140 mg KOH/g andfurther particularly 50 to 120 mg KOH/g. The total acid value of theacid value based on the monomer (e) and the acid value based on themonomer (b) falls preferably in a range of usually 100 to 200 mg KOH/g,particularly 130 to 180 mg KOH/g and further particularly 140 to 160 mgKOH/g. Further, the monomer (c) falls suitably in a range of usually 10to 80% by weight, particularly 20 to 70% by weight and furtherparticularly 30 to 60% by weight based on the total amount of themonomers (e), (b) and (c). On the other hand, the monomer (d) is usedpreferably in a range of usually 100 parts by weight or less,particularly 1 to 50 parts by weight and further particularly 5 to 40parts by weight per 100 parts by weight of the total amount of themonomers (e), (b) and (c).

[0064] The component (E) thus obtained has preferably a hydroxyl valuefalling in a range of usually 0 to 50 mg KOH/g, particularly 3 to 40 mgKOH/g and a weight average molecular weight falling in a range of 2000to 50000, particularly 3000 to 25000.

[0065] A blending amount of the component (E) in the present composition1 falls suitably in a range of usually 0 to 30 parts by weight,particularly 0 to 20 parts by weight and further particularly 1 to 15parts by weight per 100 parts by weight of the total solid matter of thecomponent (A) and the component (B).

[0066] The present composition 1 is excellent in a storage stability andan electrostatic coating property and can form a coating film which isexcellent in a scratch resistance, a hardness, a heat yellowingresistance and an acid resistance, and therefore it can advantageouslybe used as a top coating material for car bodies to which the abovecoating film performances are required, for example, a solid colorcoating material, a metallic coating material, a light coherent coatingmaterial and a clear coating material, among them, a thermosetting cleartop coating material.

Present Composition 2

[0067] The present composition 2 provided by the present invention is acurable resin composition comprising:

[0068] (D) a carboxyl group-containing acryl resin having (a) a carboxylgroup originating in a carboxyl group-containing polymerizableunsaturated monomer selected from acrylic acid, methacrylic acid, maleicacid and itaconic acid and (b) a carboxyl group originating in acarboxyl group-containing polymerizable unsaturated monomer having apolymerizable carbon-carbon double bond, a carboxyl group separated fromthe double bond by at least 6 carbon atoms and (e) a carboxyl grouporiginating in a semi-esterification product of a polymerizableunsaturated dibasic acid anhydride,

[0069] (B) an epoxy group-containing acryl resin and

[0070] (C) a curing catalyst.

[0071] The same ones as the component (B) and the component (C) eachdescribed above in the present composition 1 can be used as thecomponent (B) (epoxy group-containing acryl resin) and the component (C)(curing catalyst) each described above constituting the presentcomposition 2.

[0072] Accordingly, the carboxyl group-containing acryl resin (D)described above shall be described below in further details.

[0073] Carboxyl Group-Containing Acryl Resin (D)

[0074] The carboxyl group-containing acryl resin (hereinafter referredto as the “component (D)”) constituting the present composition 2 is anacryl resin having (a) a carboxyl group originating in a carboxylgroup-containing polymerizable unsaturated monomer selected from acrylicacid, methacrylic acid, maleic acid and itaconic acid, (b) a carboxylgroup originating in a carboxyl group-containing polymerizableunsaturated monomer having a polymerizable carbon-carbon double bond anda carboxyl group separated from the double bond by at least 6 carbonatoms and (e) a carboxyl group originating in a semi-esterificationproduct of a polymerizable unsaturated dibasic acid anhydride.

[0075] The component (D) can be obtained by copolymerizing (a) acarboxyl group-containing polymerizable unsaturated monomer selectedfrom acrylic acid, methacrylic acid, maleic acid and itaconic acid, (b)a carboxyl group-containing polymerizable unsaturated monomer having apolymerizable carbon-carbon double bond and a carboxyl group separatedfrom the double bond by at least 6 carbon atoms, (e) asemi-esterification product of a polymerizable unsaturated dibasic acidanhydride and (c) an acryl base monomer and, if necessary, (d) the otherpolymerizable unsaturated monomer than the above monomers by aconventional solution radical polymerization method.

[0076] The same ones as the monomer (a), the monomer (b), the monomer(c) and the monomer (d) each described above in the present composition1 can be used as the monomer (a), the monomer (b), the monomer (c) andthe monomer (d) among the above monomers.

[0077] On the other hand, the semi-esterification product (e) of apolymerizable unsaturated dibasic acid anhydride can be produced, to bespecific, by subjecting an acid anhydride group of a compound having atleast one polymerizable carbon-carbon double and at least one cyclicacid anhydride group in a molecule to ring-opening reaction withmonoalcohol to produce one free carboxyl group (—COOH) and onecarboxylic acid ester group (—COOR) per one acid anhydride group.

[0078] The compound having at least one polymerizable carbon-carbondouble and at least one cyclic acid anhydride group in a moleculeincludes, for example, maleic anhydride and itaconic anhydride. Themonoalcohol can have 1 to 12, preferably 1 to 7 carbon atoms andincludes, for example, methanol, ethanol, propanol, butanol, methylcellosolve and ethyl cellosolve. The semi-esterification of the cyclicacid anhydride group-containing compound with the monoalcohol can becarried out by a conventionally known method. The abovesemi-esterification can be carried out before copolymerizing the monomer(a), the monomer (b), the monomer (c) and the monomer (d) or can becarried out as well after the copolymerization.

[0079] The use proportions of the respective monomers of the monomer(a), the monomer (b), the monomer (e), the monomer (c) and the monomer(d) in the copolymerization described above shall not strictly berestricted and can optionally be selected according to the use purposesof the present composition 2. In general, the monomer (a) can be used insuch a proportion that the acid value based on the monomer (a) of thecomponent (D) formed falls in a range of 30 to 150 mg KOH/g,particularly 40 to 120 mg KOH/g and further particularly 50 to 100 mgKOH/g, and the monomer (b) can be used in such a proportion that theacid value based on the monomer (b) of the component (D) formed falls ina range of 30 to 170 mg KOH/g, particularly 40 to 140 mg KOH/g andfurther particularly 50 to 120 mg KOH/g. Also, the semi-esterificationproduct (e) is used preferably in such a proportion that the acid valuebased on the semi-esterification product (e) of the component (D) formedfalls in a range of 1 to 60 mg KOH/g, particularly 5 to 50 mg KOH/g andfurther particularly 10 to 40 mg KOH/g. Further, the total acid value ofthe acid value based on the monomer (a), the acid value based on themonomer (b) and the acid value based on the monomer (e) falls preferablyin a range of usually 100 to 200 mg KOH/g, particularly 130 to 180 mgKOH/g and further particularly 140 to 170 mg KOH/g. Also, the monomer(c) falls suitably in a range of usually 10 to 80% by weight,particularly 20 to 70% by weight and further particularly 30 to 60% byweight based on the total amount of the monomers (a), (b), (c) and (e).On the other hand, the monomer (d) is used preferably in a range ofusually 100 parts by weight or less, particularly 1 to 50 parts byweight and further particularly 5 to 40 parts by weight per 100 parts byweight of the total amount of the monomers (a), (b), (c) and (e).

[0080] The component (D) thus obtained has preferably a hydroxyl valuefalling in a range of usually 0 to 50 mg KOH/g, particularly 5 to 40 mgKOH/g and a weight average molecular weight falling in a range of 2000to 50000, particularly 3000 to 25000.

[0081] In producing the component (D) by using the monomer (a), themonomer (b), the monomer (e) and the monomer (c) and, if necessary, thepolymerizable monomer (d) and copolymerizing them, the plural monomers(b) in which an atomic group present between a polymerizablecarbon-carbon double bond and a carboxyl group has a carbon atom numberof at least 6, preferably 6 to 25 and in which the carbon atom numbersare different from each other can be used in combination, if necessary,as the monomer (b).

[0082] A difference in the carbon atom numbers of the above atomicgroups present in the plural monomers (b) in which the above carbon atomnumbers are different from each other falls preferably in a range ofusually at least 1, particularly 2 to 10. Thus, assuming that themonomer in which an atomic group has a small carbon atom number is (b-1)and that the monomer in which an atomic group has a large carbon atomnumber is (b-2), the atomic group present in the monomer (b-2) haspreferably a carbon atom number falling in a range of 10 to 25. On theother hand, the monomer in which an atomic group has a smaller carbonatom number by at least one, particularly 2 to 10 than that of the abovemonomer is preferably used as the monomer (b-1).

[0083] That is, capable of being also used as the component (D) is acarboxyl group-containing acryl resin obtained by using (a) the carboxylgroup-containing polymerizable unsaturated monomer selected from acrylicacid, methacrylic acid, maleic acid and itaconic acid, (b-1) thecarboxyl group-containing polymerizable unsaturated monomer in which anatomic group present between a polymerizable carbon-carbon double bondand a carboxyl group has a smaller carbon atom number by at least one,particularly 2 to 10 than that of the monomer (b-2) described below,(b-2) the carboxyl group-containing polymerizable unsaturated monomer inwhich an atomic group present between a polymerizable carbon-carbondouble bond and a carboxyl group has a carbon atom number of 10 to 25,(e) the semi-esterification product and (c) the acryl base monomer and,if necessary, (d) the other polymerizable unsaturated monomer than themonomers described above and copolymerizing them. In this respect, a useproportion of the monomer (b-1) and the monomer (b-2) shall not strictlybe restricted. In general, that of the monomer (b-1) falls suitably in arange of 10 to 90% by weight, particularly 30 to 70% by weight based onthe total amount of the monomer (b-1) and the monomer (b-2), and that ofthe monomer (b-2) falls suitably in a range of 90 to 10% by weight,particularly 70 to 30% by weight.

[0084] Further, it is possible that prepared are the plural monomers (b)in which an atomic group present between a polymerizable carbon-carbondouble bond and a carboxyl group has a carbon atom number of at least 6,preferably 6 to 25 and in which the carbon atom numbers are differentfrom each other, for example, the monomer (b-1) and the monomer (b-2)each described above; the monomer (b-1) and the monomer (b-2) each arecopolymerized separately with the monomer (a), the semi-esterificationproduct (e) and the monomer (c) and, if necessary, the other monomer (d)than the monomers described above to produce plural acryl resins (D);and they are used in a mixture. To be specific, capable of being used asthe component (D) is a mixture of a carboxyl group-containing acrylresin (D-1) obtained by using in combination, the monomer (a), themonomer (b-1), the semi-esterification product (e) and the monomer (c)and, if necessary, the other monomer (d) than the monomers describedabove and copolymerizing them and a carboxyl group-containing acrylresin (D-2) obtained by using in combination, the monomer (a), themonomer (b-2), the semi-esterification product (e) and the monomer (c)and, if necessary, the other monomer (d) than the monomers describedabove and copolymerizing them.

[0085] The proportions of the respective monomers constituting the acrylresin (D-1) and the acryl resin (D-2) can be those described above.Further, in respect to a mixed proportion of both of these resins, thatof the acryl resin (D-1) falls suitably in a range of 10 to 90% byweight, particularly 20 to 80% by weight based on the total solid matteramount of the resins (D-1) and (D-2), and the acryl resin (D-2) fallssuitably in a range of 90 to 10% by weight, particularly 80 to 20% byweight.

[0086] The present composition 2 can be prepared by mixing the component(D), the component (B) and the component (C) each described above in anorganic solvent. The mixing proportions of these respective componentscan optionally be selected according to the use purposes of the presentcomposition 2; in general, that of the component (D) falls suitably in arange of usually 20 to 80% by weight, particularly 30 to 70% by weightand further particularly 35 to 65% by weight based on the total solidmatter weight of the component (D) and the component (B); that of thecomponent (B) falls suitably in a range of usually 80 to 20% by weight,particularly 70 to 30% by weight and further particularly 65 to 35% byweight; and that of the component (C) falls preferably in a range ofusually 0.1 to 5 parts by weight, particularly 0.5 to 3 parts by weightand further particularly 1 to 2.5 parts by weight per 100 parts byweight of the total solid matter of the component (D) and the component(B).

[0087] The present composition 2 can be blended, if necessary, with ahydroxyl group-containing polyester resin, a solid color pigment, ametallic pigment, a light coherent pigment, an extender pigment, a UVabsorber, a light stabilizer, a coated face-controlling agent and aprecipitation inhibitor in addition to the component (A), the component(B) and the component (C).

[0088] The present composition 2 is excellent in a storage stability andan electrostatic coating property and can form a coating film which isexcellent in a scratch resistance, a hardness, a heat yellowingresistance and an acid resistance, and therefore it can advantageouslybe used as a top coating material for car bodies to which the abovecoating film performances are required, for example, a solid colorcoating material, a metallic coating material, a light coherent coatingmaterial and a clear coating material, among them, a thermosetting cleartop coating material.

EXAMPLES

[0089] The present invention shall more specifically be explained belowwith reference to examples and comparative example. Parts and percentagein the blending amounts are based on weight in principle, and a filmthickness of the coating films is that of the cured coating film.

[0090] 1. Preparation of Sample

[0091] (1) Production of a carboxyl group-containing polymerizableunsaturated monomer having a polymerizable carbon-carbon double bond anda carboxyl group separated from the double bond by at least 6 carbonatoms:

Production Example 1

[0092] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 27 parts of “Uker Ester EEP” (trade name,hydrocarbon base organic solvent, manufactured by Union Carbide Co.,Ltd.), 101 parts of succinic acid and 0.1 part of hydroquinonemonomethyl ether (polymerization inhibitor) and heated to 110° C. on amantle heater. Then, 144 parts (mole ratio: OH/succinic acid=1/1.01) of4-hydroxybutyl acrylate was dropwise added thereto in 2 hours, and thenthe solution was ripened for one hour to obtain a carboxylgroup-containing polymerizable unsaturated monomer (b-1).

Production Example 2

[0093] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 57.5 parts of“Uker Ester EEP”, 101 partsof succinic acid and 0.1 part of hydroquinone monomethyl ether(polymerization inhibitor) and heated to 110° C. on a mantle heater.Then, 130 parts (mole ratio: OH/succinic acid=1/1.01) of hydroxyethylmethacrylate was dropwise added thereto in 2 hours, and then thesolution was ripened for 3 hours to obtain a carboxyl group-containingpolymerizable unsaturated monomer (b-2).

Production Example 3

[0094] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 124 parts of “Uker Ester EEP”, 156 partsof hexahydrophthalic anhydride and 0.1 part of hydroquinone monomethylether (polymerization inhibitor) and heated to 110° C. on a mantleheater. Then, 342 parts (mole ratio: OH/hexahydrophthalicanhydride=1/1.01) of “Praxel FA2” (2 moles of a ring-openedε-caprolactone chain-containing polymerizable unsaturated monomer havinga hydroxyl group at an end, manufactured by Daicel Chemical Ind. Co.,Ltd.) was dropwise added thereto in 2 hours, and then the solution wasripened for one hour to obtain a carboxyl group-containing polymerizableunsaturated monomer (b-3).

[0095] (2) Production of acryl resin (A) having a carboxyl grouporiginating in the carboxyl group-containing polymerizable unsaturatedmonomer (a) and a carboxyl group originating in the carboxylgroup-containing polymerizable unsaturated monomer (b):

Production Example 4

[0096] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 900 parts of “Swasol 1000” (trade name,hydrocarbon base organic solvent, manufactured by Cosmo Petroleum Co.,Ltd.) and 900 parts of“Uker Ester EEP” and heated to 125° C. on a mantleheater. Then, a polymerizable monomer mixture having the followingcomposition was dropwise added thereto in 4 hours.

[0097] Polymerizable Monomer Mixture: styrene  300 parts isobutylmethacrylate 1150 parts acrylic acid  250 parts the carboxylgroup-containing polymerizable unsaturated monomer (b-1) 1450 parts andp-tert-butylperoxy-2-ethyl hexanoate  180 parts.

[0098] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour, followed by ripening itfor one hour to obtain an acryl resin solution (A-1) having a solidcontent of about 55%. This acryl resin had a weight average molecularweight of about 6000 and a total acid value of 156 mg KOH/g. Thebreakdown of the acid value was an acid value of 65 mg KOH/g based onacrylic acid (carboxyl group-containing polymerizable monomer (a)) andan acid value of 91 mg KOH/g based on the carboxyl group-containingmonomer (b).

Production Example 5

[0099] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 900 parts of “Swasol 1000” and 900 partsof “Uker Ester EEP” and heated to 125° C. on a mantle heater. Then, apolymerizable monomer mixture having the following composition wasdropwise added thereto in 4 hours.

[0100] Polymerizable Monomer Mixture: styrene  300 parts isobutylmethacrylate 1182 parts methacrylic acid  282 parts the carboxylgroup-containing monomer (b-2) 1236 parts and p-tert-butylperoxy-2-ethylhexanoate  180 parts.

[0101] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour, followed by ripening itfor one hour to obtain an acryl resin solution (A-2) having a solidcontent of about 55%. This acryl resin had a weight average molecularweight of about 6000 and a total acid value of 160 mg KOH/g. Thebreakdown of the acid value was an acid value of 60 mg KOH/g based onmethacrylic acid (carboxyl group-containing polymerizable unsaturatedmonomer (a)) and an acid value of 100 mg KOH/g based on the carboxylgroup-containing polymerizable unsaturated monomer (b).

Production Example 6

[0102] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 900 parts of “Swasol 1000” and 900 partsof“Uker Ester EEP” and heated to 125° C. on a mantle heater. Then, apolymerizable monomer mixture having the following composition wasdropwise added thereto in 4 hours.

[0103] Polymerizable Monomer Mixture: styrene  300 parts isobutylmethacrylate 1050 parts methacrylic acid  528 parts the carboxylgroup-containing monomer (b-3) 1122 parts and p-tert-butylperoxy-2-ethylhexanoate  180 parts.

[0104] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour. Further, the mixture wasripened for one hour to obtain an acryl resin solution (A-3) having asolid content of about 55%. This acryl resin had a weight averagemolecular weight of about 6000 and a total acid value of 160 mg KOH/g.The breakdown of the acid value was an acid value of 110 mg KOH/g basedon methacrylic acid (carboxyl group-containing polymerizable unsaturatedmonomer (a)) and an acid value of 50 mg KOH/g based on the carboxylgroup-containing polymerizable unsaturated monomer (b).

Production Example 7

[0105] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 900 parts of “Swasol 1000” and 900 partsof “Uker Ester EEP” and heated to 125° C. on a mantle heater. Then, apolymerizable monomer mixture having the following composition wasdropwise added thereto in 4 hours.

[0106] Polymerizable Monomer Mixture: styrene 300 parts isobutylmethacrylate 927 parts isobutyl acrylate 927 parts methacrylic acid 846parts and p-tert-butylperoxy-2-ethyl hexanoate 180 parts.

[0107] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour. Further, the mixture wasripened for one hour to obtain an acryl resin solution (A-4) having asolid content of about 55%. This acryl resin had a weight averagemolecular weight of about 6000 and an acid value of 160 mg KOH/g.

Production Example 8

[0108] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 900 parts of “Swasol 1000” and 900 partsof “Uker Ester EEP” and heated to 125° C. on a mantle heater. Then, apolymerizable monomer mixture having the following composition wasdropwise added thereto in 4 hours.

[0109] Polymerizable Monomer Mixture: styrene  300 parts isobutylmethacrylate  508 parts isobutyl acrylate  508 parts the carboxylgroup-containing 1683 parts monomer (b-3) and p-tert-butylperoxy-2-ethylhexanoate  180 parts.

[0110] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour, followed by ripening itfor one hour to obtain an acryl resin solution (A-5) having a solidcontent of about 55%. This acryl resin had a weight average molecularweight of about 6000 and an acid value of 160 mg KOH/g.

Production Example 9

[0111] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 680 parts of “Swasol 1000” and heated to125° C. on a mantle heater. Then, a polymerizable monomer mixture havingthe following composition was dropwise added thereto in 4 hours.

[0112] Polymerizable Monomer Mixture: styrene  700 parts maleicanhydride  600 parts isobutyl methacrylate 1100 parts the carboxylgroup-containing  600 parts monomer (b-1) and p-tert-butylperoxy-2-ethylhexanoate  240 parts.

[0113] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour. Then, the flask was oncecooled down to 60° C., and 590 parts of methanol (for opening the ring)and 5 parts of triethylamine were added thereto, followed by heating andrefluxing the solution for 6 hours. Thereafter, 391 parts of surplusmethanol was removed under reduced pressure to obtain an acryl resinsolution (A-6) having a solid content of about 55%. This acryl resin hada weight average molecular weight of about 4500, a whole acid value of157 mg KOH/g and a half acid value of 156 mg KOH/g.

Production Example 10

[0114] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 680 parts of “Swasol 1000” and heated to125° C. on a mantle heater. Then, a polymerizable monomer mixture havingthe following composition was dropwise added thereto in 4 hours.

[0115] Polymerizable Monomer Mixture: styrene  700 parts maleicanhydride  900 parts isobutyl methacrylate 1400 parts andp-tert-butylperoxy-2-ethyl hexanoate  180 parts.

[0116] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour. Then, the flask was oncecooled down to 60° C., and 885 parts of methanol (for opening the ring)and 7 parts of triethylamine were added thereto, followed by heating andrefluxing the solution for 6 hours. Thereafter, 586 parts of surplusmethanol was removed under reduced pressure to obtain an acryl resinsolution (A-7) having a solid content of about 55%. This acryl resin hada weight average molecular weight of about 4500, a whole acid value of157 mg KOH/g and a half acid value of 156 mg KOH/g.

[0117] (3) Production of epoxy group-containing acryl resin (B):

Production Example 11

[0118] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 600 parts of“Swasol 1000” and 400 parts ofdimethoxybutyl acetate and heated to 140° C. on a mantle heater. Then, apolymerizable monomer mixture having the following composition wasdropwise added thereto in 4 hours.

[0119] Polymerizable Monomer Mixture: styrene 100 parts isobutylacrylate 250 parts isobornyl acrylate 250 parts glycidyl methacrylate900 parts 4-hydroxybutyl acrylate 500 parts and2,2′-azobis(2-methylbutyronitrile) 120 parts.

[0120] Then, the mixture was ripened for 30 minutes, and a mixture of 10parts of 2,2′-azobis(2-methylbutyronitrile) and 300 parts of “Swasol1000” was dropwise added thereto in one hour to obtain an acryl resinsolution (B-1) having an epoxy group and a hydroxyl group in a moleculeand having a solid content of about 60%. This acryl resin having anepoxy group had a weight average molecular weight of 3000, an epoxyequivalent of 609 and a hydroxyl value of 97 mg KOH/g.

Production Example 12

[0121] A flask of 5 liter equipped with a stirrer, a thermometer and acooling tube was charged with 900 parts of “Swasol 1000” and 900 partsof“Uker Ester EEP” and heated to 125° C. on a mantle heater. Then, apolymerizable monomer mixture having the following composition wasdropwise added thereto in 4 hours.

[0122] Polymerizable Monomer Mixture: styrene  300 parts isobutylmethacrylate 1347 parts acrylic acid  192 parts the carboxylgroup-containing  912 parts monomer (b-1) a methanol-semi-esterifiedproduct of  249 parts maleic anhydride and p-tert-butylperoxy-2-ethylhexanoate  180 parts.

[0123] Then, the mixture was ripened for 30 minutes, and a mixture of 15parts of p-tert-butylperoxy-2-ethyl hexanoate and 80 parts of “Swasol1000” was dropwise added thereto in one hour, followed by ripening itfor one hour to obtain an acryl resin solution (D-1) having a solidcontent of about 55%. This acryl resin had a weight average molecularweight of about 6000 and a total acid value of 156 mg KOH/g. Thebreakdown of the acid value was an acid value of 50 mg KOH/g based onacrylic acid (carboxyl group-containing polymerizable monomer (a)), anacid value of 70 mg KOH/g based on the carboxyl group-containingpolymerizable monomer (b) and an acid value of 70 mg KOH/g based on themethanol-semi-esterified product of maleic anhydride.

[0124] (4) Production of coating material (WB-1) for water-based colorbase coat:

Production Example 13 Preparation of Acryl Resin Aqueous Dispersion(W-1)

[0125] A reactor was charged with 140 parts of deionized water, 2.5parts of “NEWCol 707SF” (trade name, surfactant, solid content: 30%,manufactured by Nippon Nyukazai Co., Ltd.) and one part of the followingmonomer mixture (1) and stirred and mixed in nitrogen flow, and 3 partsof 3% ammonium persulfate was added at 60° C. Then, after elevating thetemperature to 80° C., a monomer emulsion comprising 79 parts of themonomer mixture (1), 2.5 parts of “NEWCol 707SF”, 4 parts of 3% ammoniumpersulfate and 42 parts of deionized water was added to the reactor in 4hours by means of a quantitative pump. After finishing addition, thesolution was ripened for one hour.

[0126] Monomer Mixture (1): methyl methacrylate 55 parts styrene 10parts n-butyl acrylate  9 parts 2-hydroxyethyl acrylate  5 parts andmethacrylic acid  1 part.

[0127] Next, the temperature of the inside of the reactor describedabove was maintained at 80° C., and 20.5 parts of the following monomermixture (2) and 4 parts of 3% ammonium persulfate were dropwise addedparallel at the same time in 1.5 hour. After finishing addition, thesolution was ripened for one hour and filtered at 30° C. through a nyloncloth of 200 mesh. Deionized water was further added thereto, and the pHwas controlled to 7.5 by N,N-dimethylethanolamine to obtain an acrylresin aqueous dispersion (W-1) having an average particle diameter of0.1 μm, a Tg (glass transition temperature) of 46° C. and a non-volatilematter content of 20%.

[0128] Monomer Mixture (2): methyl methacrylate   5 parts n-butylacrylate   7 parts 2-ethylhexyl acrylate   5 parts methacrylic acid   3parts and “NEWCol 707SF” 0.5 part.

Production Example 14 Preparation of Acryl Resin Aqueous Dispersion(W-2)

[0129] A reactor was charged with 60 parts of ethylene glycol monobutylether and 15 parts of isobutyl alcohol and heated to 115° C. in nitrogenflow. After reaching 115° C., a mixture of n-butyl acrylate 26 parts,methyl methacrylate 47 parts, styrene 10 parts, 2-hydroxyethylmethacrylate 10 parts, acrylic acid 1 part 6 parts,azobisisobutyronitrile 1 part and butyl cellosolve 115 parts was addedin one hour, and then the solution was ripened for 30 minutes andfiltered at 50° C. through a nylon cloth of 200 mesh. The resultingreaction product had an acid value of 48 mg KOH/g, a viscosity Z4(Gardner bubble viscometer), a non-volatile matter content of 55% and aTg of 45° C. This was equivalently diluted with N,N-dimethylethanol, anddeionized water was added thereto, whereby an acryl resin aqueousdispersion (W-2) having a non-volatile matter content of 50% wasobtained.

Production Example 15 Coating Material (WB-1) for Water-Based Color BaseCoat

[0130] Mixed were 275 parts of the acryl resin aqueous dispersion (W-1)described above having a non-volatile matter content of 20%, 40 parts ofthe acryl resin aqueous dispersion (W-2) described above having anon-volatile matter content of 50%, 25 parts of “Cymel 350” (trade name,melamine resin, manufactured by Mitsui Toatsu Chemical Co., Ltd.), 20parts of “Alumi Paste AW-500B” (trade name, metallic pigment,manufactured by Asahi Kasei Metals Co., Ltd.), 20 parts of ethyleneglycol monobutyl ether and 253 parts of deionized water, and “TicsolK-130B” (trade name, thickener, manufactured by Kyoei Yushi ChemicalInd. Co., Ltd.) was added thereto to control the viscosity to 3000 Pa·s(millipascal second) measured by means of a B type viscometer (rotorrevolution: 6 rpm), whereby a coating material (WB-1) for a water-basedcolor base coat having a non-volatile matter content of about 19% wasobtained.

[0131] 2. Examples and Comparative Examples

[0132] A resin mixed solution was prepared in a composition (shown interms of a solid matter amount ratio) shown in the following Table 1,and a green coating material obtained by adding 2 parts of an equivalentblended matter (curing catalyst (C)) of tetrabutylammonium bromide andmonobutylphosphoric acid, 1 part of “Tinuvin 900” (trade name, UVabsorber, manufactured by Ciba Geigy Co., Ltd.) and 0.1 part of “BYK300” (trade name, surface controlling agent, manufactured by Bic ChemieCo., Ltd.) per 100 parts of the resin mixed solution was diluted withn-butanol and controlled to a viscosity of 30 seconds (Ford cup #4/20°C.) to obtain curable resin compositions (including compositions forcomparison) (clear top coating materials). TABLE 1 Example ComparativeExample 1 2 1 2 3 4 Component Name A-1 A-2 A-3 A-4 A-5 A-6 A-7 (A)Amount 50 25 25 50 50 50 50 Component Name B-1 B-1 B-1 B-1 B-1 B-1 (B)Amount 50 50 50 50 50 50 Component (C):  2  2  2  2  2  2 catalyst

Example 3

[0133] The same procedure as in Example 1 was carried out to obtain acurable resin composition, except that “(A-1) 50 parts” was changed to“(D-1) 50 parts”.

[0134] 3. Performance Test

[0135] An epoxy resin base cationically electrodepositable coatingmaterial was electrodepositably coated on a dull steel plate having athickness of 0.8 mm subjected to chemical conversion treatment with zincphosphate so that a film thickness was about 20 μm and heated at 170° C.for 20 minutes to cure a coating film. Further, the coated face wasrubbed with a #400 sand paper and defatted by wiping with petroleumbenzene, and then an intermediate coating surfacer for automobiles(polyester resin melamine resin base organic solvent type) was coated bymeans of an air spray so that a film thickness was about 25 μm and curedby heating at 140° C. for 30 minutes. Further, the coated face waswater-rubbed with a #400 sand paper, dripped, dried and defatted bywiping with petroleum benzene to obtain a material for testing (materialto be coated).

[0136] The coating material (WB-1) for a water-based color base coatprepared above was coated on the surface of the above material to becoated so that a film thickness was 20 μm and dried at a roomtemperature for 5 minutes, and then the curable resin compositions(clear top coating materials) obtained in the examples and thecomparative examples were coated on the non-cured coated face so that afilm thickness was about 40 μm and heated at 140° C. for 30 minutes tocure both coating films at the same time, whereby a double layer topcoating film was cured.

[0137] The top coating films on the coated test plates thus obtainedwere subjected to various performance tests. The results thereof areshown in Table 2.

[0138] The performance tests shown in Table 2 were carried out by thefollowing methods.

[0139] Electrical Resistance Value:

[0140] An electrical resistance value (20° C.) of the curable resincomposition prepared by mixing the respective components shown in Table1 and diluting the mixture with n-butanol to control a viscosity to 30seconds (Ford cup #4/20° C.) was measured by means of “Lanbarg 234 typePaint Conducting Tester” (trade name, manufactured by Lanbarg Co.,Ltd.). A shows that the electrical resistance value is 0.3 MΩ or more,and B shows that the electrical resistance value is less than 0.3 MΩ. Ifthe resistance value is less than 0.3 MΩ, short circuit is caused inelectrostatically coating in a certain case, and therefore it is notpreferred.

[0141] Yellowing Property:

[0142] The coated test plate described above obtained by heating andcuring was further heated (over-baked) at 160° C. for one hour, and thenthe degree of a discoloration in the coated face was visually observed.A shows that discoloration is not observed at all; B shows thatyellowing is observed a little; and C shows that yellowing is notablyobserved.

[0143] Hardness:

[0144] It is a hardness of the double layer coating film, and the tuconhardness at 20° C. was measured. It is shown that the larger thenumerical value is, the harder the coating film is. A shows 10 or more;B shows 5 to less than 10; and C shows 1 to less than 5.

[0145] Car Wash Scratching Property:

[0146] The coated test plate described above was stuck on an outsideroof face of a car with the coated face turned to the outside andsubjected continuously 15 times to car washing by means of a car-washingmachine, and then the coated face of the test plate was visuallyobserved. “P020 FVVRC” (trade name, manufactured by Yasui Sangyo Co.,Ltd.) was used as the car-washing machine. A shows that scratches arescarcely observed to be caused; B shows that scratches are a littleobserved to be caused; and C shows that many scratches are observed tobe caused.

[0147] Storage Stability

[0148] The curable resin composition (clear top coating material) whichwas control to a viscosity of 30 seconds (Ford cup #4/20° C.) was storedat 40° C. for 2 weeks, and then the degree of a rise in the viscositywas observed. A shows that the viscosity after storage is 40 seconds(Ford cup #4/20° C.) or less; B shows that the viscosity after storageis 40 to 60 seconds (Ford cup #4/20° C.); and C shows that the viscosityafter storage is 60 seconds or more (Ford cup #4/20° C.). TABLE 2Example Comparative Example 1 2 3 1 2 3 4 Electrical resistance A A A AA B B value Yellowing property A A A A A B B Hardness A A A A C A A Carwash scratching A A A C A A C property Storage stability A A A A A B B

1. A curable resin composition comprising: (A) a carboxylgroup-containing acryl resin having (a) a carboxyl group originating ina carboxyl group-containing polymerizable unsaturated monomer selectedfrom acrylic acid, methacrylic acid, maleic acid and itaconic acid and(b) a carboxyl group originating in a carboxyl group-containingpolymerizable unsaturated monomer having a polymerizable carbon-carbondouble bond and a carboxyl group separated from the double bond by atleast 6 carbon atoms, (B) an epoxy group-containing acryl resin and (C)a curing catalyst.
 2. The resin composition as described in claim 1,wherein the monomer (b) is a carboxyl group-containing polymerizableunsaturated monomer having a polymerizable carbon-carbon double bond anda carboxyl group separated from the double bond by 6 to 25 carbon atoms.3. The resin composition as described in claim 1, wherein the component(A) is obtained by copolymerizing the carboxyl group-containingpolymerizable unsaturated monomer (a), the carboxyl group-containingpolymerizable unsaturated monomer (b) and an acryl base monomer (c) and,if necessary, other polymerizable monomer (d).
 4. The resin compositionas described in claim 3, wherein plural carboxyl group-containingpolymerizable unsaturated monomers in which atomic groups presentbetween a polymerizable carbon-carbon double bond and a carboxyl grouphave carbon atom numbers different from each other are used as thecarboxyl group-containing polymerizable unsaturated monomer (b).
 5. Theresin composition as described in claim 3, wherein plural carboxylgroup-containing polymerizable unsaturated monomers in which atomicgroups present between a polymerizable carbon-carbon double bond and acarboxyl group have carbon atom numbers different from each other areseparately used as the carboxyl group-containing polymerizableunsaturated monomer (b), and the resulting plural carboxylgroup-containing acryl resins are used as the component (A).
 6. Theresin composition as described in claim 1, wherein the component (A) hasan acid value of 30 to 150 mg KOH/g based on the monomer (a).
 7. Theresin composition as described in claim 1, wherein the component (A) hasan acid value of 30 to 170 mg KOH/g based on the monomer (b).
 8. Theresin composition as described in claim 1, wherein the component (A) hasa total acid value of 100 to 200 mg KOH/g.
 9. A curable resincomposition comprising: (D) a carboxyl group-containing acryl resinhaving (a) a carboxyl group originating in a carboxyl group-containingpolymerizable unsaturated monomer selected from acrylic acid,methacrylic acid, maleic acid and itaconic acid, (b) a carboxyl grouporiginating in a carboxyl group-containing polymerizable unsaturatedmonomer having a polymerizable carbon-carbon double bond and a carboxylgroup separated from the double bond by at least 6 carbon atoms and (e)a carboxyl group originating in a semi-esterification product of apolymerizable unsaturated dibasic acid anhydride, (B) an epoxygroup-containing acryl resin and (C) a curing catalyst.
 10. The resincomposition as described in claim 9, wherein the monomer (b) is acarboxyl group-containing polymerizable unsaturated monomer having apolymerizable carbon-carbon double bond and a carboxyl group separatedfrom the double bond by 6 to 25 carbon atoms.
 11. The resin compositionas described in claim 9, wherein the component (D) is obtained bycopolymerizing the carboxyl group-containing polymerizable unsaturatedmonomer (a), the carboxyl group-containing polymerizable unsaturatedmonomer (b), the semi-esterification product (e) of a polymerizableunsaturated dibasic acid anhydride and an acryl base monomer (c) and, ifnecessary, other polymerizable monomer (d).
 12. The resin composition asdescribed in claim 11, wherein plural carboxyl group-containingpolymerizable unsaturated monomers in which atomic groups presentbetween a polymerizable carbon-carbon double bond and a carboxyl grouphave carbon atom numbers different from each other are used as thecarboxyl group-containing polymerizable unsaturated monomer (b).
 13. Theresin composition as described in claim 11, wherein plural carboxylgroup-containing polymerizable unsaturated monomers in which atomicgroups present between a polymerizable carbon-carbon double bond and acarboxyl group have carbon atom numbers different from each other areseparately used as the carboxyl group-containing polymerizableunsaturated monomer (b), and the resulting plural carboxylgroup-containing acryl resins are used as the component (D).
 14. Theresin composition as described in claim 9, wherein the component (D) hasan acid value of 30 to 150 mg KOH/g based on the monomer (a).
 15. Theresin composition as described in claim 9, wherein the component (D) hasan acid value of 30 to 170 mg KOH/g based on the monomer (b).
 16. Theresin composition as described in claim 9, wherein the component (D) hasan acid value of 1 to 60 mg KOH/g based on the semi-esterificationproduct (e).
 17. The resin composition as described in claim 9, whereinthe component (D) has a total acid value of 100 to 200 mg KOH/g.
 18. Theresin composition as described in claim 1 or 9, wherein the component(B) is obtained by copolymerizing an epoxy group-containingpolymerizable monomer and an acryl base monomer and, if necessary, ahydroxyl group-containing polymerizable monomer and/or otherpolymerizable monomer.
 19. The resin composition as described in claim 1or 9, wherein the component (B) has a weight average molecular weight of2000 to 50000 and an epoxy equivalent of 50 to
 1000. 20. The resincomposition as described in claim 1 or 9, wherein the component (C)comprises a combination of a quaternary ammonium salt and a phosphatebase compound.
 21. The resin composition as described in claim 1,comprising 20 to 80% by weight of the component (A) and 80 to 20% byweight of the component (B) based on the total solid matter weight ofthe component (A) and the component (B).
 22. The resin composition asdescribed in claim 1, comprising 0.1 to 5 parts by weight of thecomponent (C) per 100 parts by weight of the total solid matter of thecomponent (A) and the component (B).
 23. The resin composition asdescribed in claim 9, comprising 20 to 80% by weight of the component(D) and 80 to 20% by weight of the component (B) based on the totalsolid matter weight of the component (D) and the component (B).
 24. Theresin composition as described in claim 1, comprising 0.1 to 5 parts byweight of the component (C) per 100 parts by weight of the total solidmatter of the component (D) and the component (B).
 25. A top coatingmaterial comprising the resin composition as described in claim 1 or 9.